The present invention generally relates to automated lead-acid battery production equipment and in particular to a method and apparatus for automatically removing flash from weld beads on industrial lead-acid batteries cells.
Typically, during the construction of a plastic cased cell, for example of a type which form an industrial lead-acid battery, various internal elements of the cell are fitted into a plastic cell container or jar prior to sealing a plastic cell cover to that container or jar. Unlike other general heat sealing operations, the seals which are produced between the cell jar and the cell jar cover must be unusually strong and liquid tight. A failure in this seal at any point is likely to result in the leakage of acid into the environment. Finally, these seals must be of sufficient strength to withstand extreme vibration and great stress, not only due to the weight of the lead battery plates and acid electrolyte, but also by reason of the intended end uses to which the cells and the resultant storage batteries are normally subjected.
For the above described reasons, it is of particular importance to obtain even melting of those portions of the cell cover and the plastic container which are to form the heat seal between these two elements. Normally, this operation is accomplished by simultaneously melting portions of the plastic cell cover and plastic cell container using a single, heated platen, and then quickly removing the platen and pressing the container and cover together under pressure for a sufficient length of time to allow the hardening of the melted material. This operation results in the formation of a "weld bead" which normally has flash, or unwanted plastic material, extending outwardly beyond the outer surfaces of the cell container.
This flash is undesirable for a number of reasons. First, excessive flash on the outer surfaces of the container causes dimensional irregularities which are particularly undesireable in industrial battery cells since industrial batteries are normally constructed by placing a plurality of cells into a battery tray under fairly strict dimensional tolerance limitations. Consequently, a cell having excessive flash on the outer surfaces thereof, may not fit into the battery tray along with the other cells. Even if the flash on a particular cell container is not extensive, if this flash appears on all cell containers to be placed within a particular battery tray, the cumulative dimensional irregularities may prove to be prohibitive.
Second, the flash formed on the external surfaces of the battery cell adversely affects its appearance. Third, the presence of flash is very often indicative of weakened welds which are non-uniform in quality and strength along their length. These weaknesses, or potential weaknesses, can be aggravated by abrasion of the flash fragments during handling, installation or use.